Extract answers from Structs module

lib/koans/08_structs.ex

@@ -5,38 +5,31 @@ defmodule Structs do
     defstruct [:name, :age ]
   end
 
-  koan "structs are defined and named after a module" do
-    person = %Person{}
-    assert person == %Person{}
-  end
-
   koan "you can access the fields of a struct" do
     nobody = %Person{}
-    assert nobody.age == nil
-    assert nobody.name == nil
+    assert nobody.age == :__
   end
 
   koan "You can pass initial values to structs" do
     joe = %Person{name: "Joe", age: 23}
-    assert joe.age == 23
-    assert joe.name == "Joe"
+    assert joe.name == :__
   end
 
   koan "update fields with the pipe '|' operator" do
     joe = %Person{name: "Joe", age: 23}
     older = %{ joe | age: joe.age + 10}
-    assert  older.age == 33
+    assert  older.age == :__
   end
 
   koan "the original struct is not affected by updates" do
     joe = %Person{name: "Joe", age: 23}
     assert %{ joe | age: joe.age + 10}.age == 33
-    assert joe.age == 23
+    assert joe.age == :__
   end
 
   koan "you can pattern match into the fields of a struct" do
     %Person{age: age} = %Person{age: 22, name: "Silvia"}
-    assert age == 22
+    assert age == :__
   end
 
   defmodule Plane do
@@ -44,16 +37,14 @@ defmodule Structs do
   end
 
   koan "or onto the type of the struct itself" do
-    assert is_a_plane(%Plane{passengers: 417, maker: :boeing})
-    refute is_a_plane(%Person{age: 22, name: "Silvia"})
+    assert is_a_plane(%Plane{passengers: 417, maker: :boeing}) == :__
   end
 
   def is_a_plane(%Plane{}), do: true
-  def is_a_plane(_), do: false
 
   koan "are basically maps" do
     silvia = %Person{age: 22, name: "Silvia"}
 
-    assert Map.fetch!(silvia, :age) == 22
+    assert Map.fetch!(silvia, :age) == :__
   end
 end

test/koans_harness_test.exs

@@ -149,6 +149,20 @@ defmodule KoansHarnessTest do
     test_all(Arithmetic, answers)
   end
 
+  test "Structs" do
+    answers = [
+      nil,
+      "Joe",
+      33,
+      23,
+      22,
+      true,
+      22,
+    ]
+
+    test_all(Structs, answers)
+  end
+
   def test_all(module, answers) do
     module.all_koans
     |> Enum.zip(answers)